Sunday, March 9, 2014

the Pennsylvania Railroad's S1 steam locomotive

As featured on a PRR calendar for 1939. The S1 class, built at the Altoona works, was a single example, numbered 6100 and nicknamed "The Big Engine". It was a one-off experiment, the longest and heaviest rigid frame reciprocating steam locomotive ever built. The streamlined Art Deco styled shell was designed by Raymond Loewy.

The S1 was the only locomotive ever built with a 6-4-4-6 wheel arrangement. It was a duplex locomotive, meaning that it had two pairs of cylinders, each driving two pairs of driving wheels. Unlike similar-looking articulated locomotive designs, the driven wheelbase of the S1 was rigid. At 140 ft 2 1⁄2 in (42.74 metres) overall, engine and tender, the S1 was also the longest reciprocating steam locomotive ever and was too big for many PRR curves. Along with wheel slippage, this limited the S1's usefulness. No further S1 were built as focus shifted to the T1 class. The last run for the S1 was in December 1945 and the engine was scrapped in 1949.

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